1. Field of the Invention
This invention relates to a data card having a substrate and a data surface region and more particularly related to a data card having or substrate and data surface region. In the preferred embodiment, the non-magnetic substrate is a glass-ceramic substrate and the data surface region comprises a magnetic storage medium having at least one layer of high density, high coercivity magnetic material for storing magnetic signals. In addition, the data storage card may further comprise a relatively hard, abradeable protective coating formed on the magnetic material layer and is selected to have a thickness between a maximum thickness which would materially attenuate magnetic signals passing between the magnetic material layer and a transducer and a minimum thickness enabling said protective coating to be abraded by usage in an ambient natural atmosphere operating environment for removing therefrom a known quantity of the protective coating.
The data card may be in the form of an encodeable card having a magnetic or optical data storage device adapted to be used as a credit card, medical identification card, identification card or the like.
The data storage device utilizes a recording medium or a data storage medium formed on a substrate capable of reliable data recording and reproduction in an ambient natural atmospheric operating environment. Traditional hard disks require a profoundly protected environment for reliable data recording and reproduction. In the preferred embodiment, the data storage device is in the form of a magnetically encodeable credit card having a data storage capability in the order of about 1 megabyte to about 500 megabytes or more.
2. Description of Prior Art
Digital data is stored in many forms. One data storage device uses spinning disks having a magnetic surface containing the digital data. The disks typically spin at a high rate of speed with the various tracks of data accessed by a radially movable data head.
Rotating a magnetic memory storage devices generally includes two elements namely, a rigid substance having a coating of magnetic media formed on at least one surface thereof. Aluminum alloys have been conventionally used as a substrate material for magnetic memo ry disks the present trend is towards smaller disk drives driven by drive motors having less torque as such, it has become necessary to develop thin light-weight rugged disks to replace the standard metal disks formed of an aluminum alloy having a cooling of magnetic media formed thereon.
Several alternatives are known in the art for replacing a standard aluminum alloy metal disk. These alternatives include glass substrates having specifically chemically tempered glass.
Also, glass-ceramic substrates have been developed. The glass-ceramic substrate composition in crystalline phase are controlled to develop specific characteristics of the glass-ceramic which enabling use of the glass-ceramic as a rigid substrate. Glass-ceramic substrate materials may have a polished surface to enhance the lubricity, optimized thermal expansion coefficients and be free of silica, such as quartz. The known glass-ceramic substrate materials are selected to have a bulk thermal expansion which is similar to that for known rigid metal substrates used for magnetic memory disks.
For example, U.S. Pat. No. 5,744,208 discloses a glass-ceramics containing lithium disilicate in tridymite. U.S. Pat. No. 5,789,056 discloses a thin film magnetic disk having a substrate made of glass or comparable rigid material.
Typical magnetic disks utilizing a glass substrate are disclosed in U.S. Pat. Nos. 6,048,466; 5,900,324; 5,824,427; 5,789,056; 5,766,727; 5,744,208; 5,569,518; 5,378,548; and 5,037,515.
It is also known in the art to provide texturing in a predetermined pattern on a substrate the adhesion of magnetic layers to the surface of a disk substrate. Typical texturing techniques and patterns are disclosed in U.S. Pat. Nos. 5,748,421; 5,725,625; 5,626,970; 5,496,606 and 4,996,622.
It is also known in the art to utilize materials other than aluminum alloy or glass for disk substrates. U.S. Pat. No. 5,492,745 discloses disks wherein a non-magnetic substrate can be formed of a metal substrate, glass substrate, ceramic substrate or a resin substrate.
U.S. Pat. Nos. 5,736,262 and 5,352,501 also disclose use of non-magnetic substrates which are textured and/or processed to enhance performance of magnetic recording mediums formed thereon.
Another type of data storage device is the credit card having a magnet stripe along one surface. However, such cards have limited storage capacity because of the nature of the magnetic stripe and the method of recording data onto the magnetic stripe.
U.S. Pat. Nos. 5,396,545 and 4,791,283 disclose typical state-of-the-art financial cards or transaction cards having a single magnetic stripe. The storage densities of single stripe magnetic cards are defined by the ANSI Standard Specifications. Prior art magnetically encoded cards may have up to three (3) data tracks as described in Table 1 below:
TABLE 1TrackDensityTargeted Application1553 bytesDesigned for Airline Use2200 bytesDesigned for Credit Card Use3535 bytesNot for General use reserved forSpecial Applications, HasRead/Write capabilityTotal Storage1,288 bytes  
A general trend presently exists to develop special purpose data cards for non-financial data applications such as for driver's licenses, building security, insurance identification, medical insurance identification, personal identification, inventory identification, baggage tags and the like.
United States Patents disclosing cards having one or more magnetic strips and/or semiconductor memory include U.S. Pat. Nos. 5,883,377; 5,844,230; 5,59,885 and 5,714,747. Certain of these cards using a semi-conductor memory have storage densities as high as 8 kilobytes.
Other known storage devices used in non-card applications, such as for example, data storage mediums in hard disk, have storage densities greater than the storage densities of the known credit cards having one or more magnetic stripes including three (3) data tracks. A data storage medium in a hard disc drive typically, has an 130 mm, 95 mm, 65 mm or 25 mm outer diameter with a hole in the middle for mounting the medium on a spindle motor. Hard disk drive medium is designed and manufactured for use as a rotating memory device with circumferential discrete data tracks. The medium, or disks, typically spin at a high rate of speed with the data tracks accessed by one or more a radially movable read/write heads.
Through a plating and/or a sputter process, various types and layers of magnetic or non-magnetic materials are deposited on a round substrate which, when used in conjunction with a data recording head, can read and write data to the disk. The layer which provides the data memory is formed of a high coercive force magnetic material. This high coercive force magnetic layer is designed for maximum signal-to-noise ratio. This is attained by circumferential texturing, which is a mechanical process of scratching or buffering the disk substrate surface to provide circumferential anisotropy of the magnetic domains. Thereafter, the magnetic material is deposited on the circumferentially treated surface using known plating and/or sputtering technology.
The disk drive manufacturer must exercise similar clean room conditions in order to avoid damaging or contaminating the medium. Contamination or damage to the medium will cause an unacceptable error rate for the disk drive. To further insure data integrity, the drive manufacturer mounts the heads and medium, commonly called a head/disk assembly, inside a sealed disk drive cavity. As the medium rotates, it generates airflow over the head/disk assembly. Particles or contamination inside the drive are captured by filters located within the air flow. Capillary tubes and/or breather filters located in the lid of disk drive are used to equalize pressure and prevent moisture from entering the head/disk assembly.
The magnetic head(s) that perform the read/write operations can indent, mark or damage the medium through shock, vibration or improper head/medium design. The medium layers are very thin and fragile, on the order of a few microinches thick, and can be easily destroyed by mechanical damage imposed by the head. Non-operating environmental conditions, such as those normally found outside a clean room or outside a disk drive, can also easily render the medium unusable. Some of these major concerns which adversely affect medium quality and usability are:                (a) Moisture, which can cause the Cobalt in the high coercive force magnetic layer to corrode which causes the medium surface to flake off or pit and compromise medium performance;        (b) Chemical contamination from out gassing of internal head/disk assembly components such as uncured epoxy and plasticizers from gaskets, and such chemical contamination can cause the head to stick to the media surface resulting in stopping the drive from spinning or causing a head/disk crash resulting in substantial loss of data;        (c) Particles inside the drive which can cause a head crash that can damage the medium beyond use;        (d) Handling damage by the disk or drive manufacturer including finger prints, scratches, and indentations which can cause nonreversible loss of data;        (e) Shock and vibration from improper drive design or use can cause a head crash that damages the medium beyond use; and        (f) Poorly designed drives can fail during drive power up cycles due to high stiction, friction, temperature/humidity conditions or improper lubricant conditions.        
A hard disk drive medium has no direct means to prevent demagnetization by stray magnetic fields should the drive medium be exposed to a stray field having sufficient magnetic field strength to erase the recorded data. Further, no surface of hard disk drive medium readily permits cleaning, and there are no known commercial hard disk drives that provide a means to clean the medium. For example, fingerprints cannot easily be removed from the surface of a hard disk drive medium.
Further, any attempts to use a hard disk drive magnetic medium outside of its intended clean and protected environment has been unsuccessful for a number of reasons, such as those discussed above.
As the demand for improved portable cards having increased memory storage capacity, such as credit cards, non-financial cards, transaction cards and the like increases, the driving factor as to the likely success or failure of an improved card is directly related to: (a) the storage densities available in such a card for storing and retrieving data; (b) the integrity of the magnetically encoded data in such a card; and (c) its ability to resist mechanical, chemical and magnetic degradation in an unprotected environment; such as in an ambient natural atmosphere operating environment in which financial and non-financial cards are used.
The magnetic disk media in known rigid disk drives are not designed to withstand even the most minor surface damage or degradation. The magnetic disk media for use inside the profoundly clean disk drive has a very hard but thin overcoat or protective layer. That overcoat or protective layer is typically diamond-like carbon on the order of 50 Angstroms to 300 Angstroms thick and is primarily used to control corrosion of the underlying cobalt based high coercivity layer. The underlying magnetic high coercivity film is also very thin, in the order of 150 to 500 Angstroms.
Since the protective layer includes at least one layer of a highly magnetic permeable material, the added thickness of this highly magnetic permeable material does not appear to increase the magnetic separation loss during read back as reported in U.S. Pat. No. 5,041,922.
The most prevalent type of media construction for use in hard disk drives is an aluminum substrate with a thick layer of Nickel Phosphor plated on the surface for polishing. This is an underlayer to the high coercivity magnetics. The Nickel Phosphor layer is typically 10 to 12 microns thick and is used to provide a material that can be subsequently polished to a smoother finish than the aluminum surface.
Hard disk drive media substrate range in thickness from 0.020 inches to 0.050 inches. Thinner substrates are desirable in order to be able to package more disks in the disk drive but have the problem of mechanical flutter, especially at high RPM. None of these substrates are bendable. A large bend radius of 20 inches will result in permanent deformation of the disk. A bend radius of less than 20 inches will result in permanent deformation as well as fracturing of the thick Nickel Phosphor layer. This fracturing of the Nickel Phosphor will propagate through the high coercivity magnetic layer rendering the media useless as a storage device.
No thick Nickel Phosphor underlayer is used on the portable card of the present invention. Therefore, fracturing problems associated with a thick Nickel Phosphor are avoided.
The portable card structure allows a card to be bendable to a degree depending upon the thickness and material of the substrate. For example, on one extreme are thick cards having a substrate formed of Zirconium. Such cards are 0.020 inches thick and can be bendable to a radius of approximately 10 inches. Another type of card uses a plastic substrate. Such cards are 0.030 inches thick and are bendable to a radius of approximately 4 inches. A thin card, such as a card having a substrate, formed of stainless steel, which is in the order of 0.005 inches thick and are bendable to a radius in excess of 4 inches without fracturing or becoming permanently deformed.
The protective coating of the present invention can be used with such cards in all forms of data storage devices, data storage sections, data storage medium a nd recording mediums. The known prior art media used for disk drive including the unabradable, thin protective coatings are not capable of being used in such portable cards.